The present invention relates to the synthesis of N-vinylformamide, and particularly, to the synthesis of N-vinylformamide using cyclic anhydride reagents.
N-vinylformamide (NVF) is a monomer with potentially useful properties in that it free-radically polymerizes to produce water-soluble poly(N-vinylformamide) (PNVF) and also undergoes controlled radical polymerization using RAFT methodology. Badesso, R. J.; Nordquist, A. F.; Pinschmidt, Jr. R. K.; and Sagl, D. J. “Hydrophilic polymers: performance with Environmental Acceptance”, Glass, E.; Ed.; America Chemical Society, Washington, D.C., 1995, p489. PNVF is probably the most practical precursor for preparation of poly(vinylamine). Because vinyl amine is unstable and hence cannot be maintained, PNVF is likely the best route to the generation of polyvinyl amine, a useful and less toxic alternative to polyacrylamide and other cationic, water-soluble polymers PNVF is easily hydrolyzed under basic or acidic conditions to form poly(vinylamine).
There are three known commercial routes to NVF. For example, BASF, at its Ludwigshafen, Germany site, reacts acetaldehyde with HCN, then formamide, forming the cyanoethyl formamide (FAN). FAN is then “cracked” to NVF plus HCN, where the latter is recycled. The BASF Ludwigshafen, Germany site is one of the few sites in the world skilled in HCN chemistry. As this highly toxic chemical cannot be transported, the process is most likely restricted to Ludwigshafen.
Mitsubishi developed a process whereby acetaldehyde is reacted with formamide to form hydroxyethyl formamide (HEF) using either acid or base catalysis. HEF is then reacted with methanol to form methoxyethyl formamide (MEF) using an acid catalyst with the loss of water. HEF is finally cracked to methanol and NVF, and the NVF purified. It has been reported that the NVF material synthesized by this method, exhibited lower than desired purity.
Air Products developed an alternative route to NVF wherein HEF is reacted with additional formamide (over a solid acid catalyst) to form the ethylidene bisformamide (BIS) plus water. BIS is then cracked (pyrolyzed) to form NVF plus formamide (wherein the latter is recycled). The NVF is then vacuum distilled. It is quite important in the operation of this process to minimize the hydrolysis of formamide (creating ammonia that fouls the catalyst) during BIS formation. Obviously the presence of water during this reaction creates problems.
It is very desirable to develop alternative routes to the synthesis of N-vinylformamide.